Display device

ABSTRACT

A display device includes a display panel and an infrared sensing module. The display panel includes an active region in which a pixel that emits light based on a data signal is disposed. The infrared sensing module transmits a first infrared light that passes through the active region and receives a second infrared light that passes through the active region to recognize an object. The wavelength of the first infrared light may have a wavelength greater than a predetermined value so that a luminance of light emitted by the pixel is not affected by operation of the infrared sensing module.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. application Ser. No.15/724,885, filed on Oct. 4, 2017 in the U.S. Patent and TrademarkOffice, which in turn claims priority under 35 U.S.C. § 119 from KoreanPatent Application No. 10-2016-0146864 filed on Nov. 4, 2016 in theKorean intellectual Property Office (KIPO), the contents of both ofwhich are herein incorporated by reference in their entireties.

1. TECHNICAL FIELD

Embodiments of the inventive concept relate generally to a displaydevice. More particularly, embodiments of the present inventive conceptrelate to a display device that includes an infrared sensor.

2. DISCUSSION OF THE RELATED ART

A display device displays an image using a pixel (or, a pixel circuit).Some display devices include an infrared sensor in a bezel (or, in anedge region) of its front surface (e.g., a surface on which the image isdisplayed). In such an arrangement, the display device can recognize anobject within a predetermined distance from the display device via theinfrared sensor. For example, the display device may transmit infraredlight, may receive reflected light that is generated by the infraredlight being reflected off of the object, may calculate a distancebetween the display device and the object based on intensity of thereflected light. Moreover, the display device may not display the imageif the calculated distance is less than a specific distance.

Generally, as the bezel of the display device decreases, the eyes of auser may focus more on the image (or, a screen of the display device).Recently, many manufacturers have reduced the size of, or eliminated thebezel altogether from the front surface of the display device. When thedisplay device does not include the bezel on the front surface of thedisplay device, the display device can use the front surface of thedisplay device more efficiently, for example, by displaying the image onan entire region of the front surface of the display device. In such acase, the infrared sensor may be relocated to another location of thedisplay device.

SUMMARY

In an embodiment, the inventive concept may provide a display devicethat can display an image on an entire region of its front surface whileincluding an infrared sensing function.

According to an embodiment of the inventive concept, a display devicemay include a display panel having a front surface and a rear surface,the display panel including an active region in which a pixel that emitslight based on a data signal is disposed; and an infrared sensing moduleconfigured to transmit infrared light including at least a firstinfrared light that passes in a first direction away from the frontsurface of the display panel and through the active region, and theinfrared sensing module is configured to receive a second infrared lightthat passes in a second direction toward the front surface of thedisplay panel and through the active region by which the infraredsensing module recognizes an object external to the display device.

According to an embodiment of the inventive concept, the infraredsensing module is arranged on a rear surface of the display panel, andthe infrared sensing module transmits the first infrared light in afirst direction that is substantially perpendicular to the front surfaceof the display panel.

The infrared sensing module may be arranged to face the rear surface ofthe display panel to transmit the first infrared light through a portionof the active region of the display panel having a lower pixel densitythan a remainder of the active region.

The display device may further include a housing having a surface thatfaces the rear surface of the display panel, and wherein the infraredsensing module is arranged between the rear surface of the display paneland the housing.

According to an embodiment of the inventive concept, the second infraredlight may include reflected light that is generated by the firstinfrared light being reflected by the object. In addition, the infraredsensing module may recognize the object based on a change of the secondinfrared light.

According to an embodiment of the inventive concept, the infraredsensing module may include at least one selected from a proximitysensor, a gesture sensor, and a fingerprint recognition sensor.According to an embodiment of the inventive concept, the first infraredlight may have a first wavelength of more than about 1200 nm.

According to an embodiment of the inventive concept, a luminance of thepixel located in the active region is unchanged when the infraredsensing module transmits the first infrared light at the wavelength ofgreater than about 1200 nm.

According to an embodiment of the inventive concept, the firstwavelength of the first infrared light may be 1300 nm.

According to an embodiment of the inventive concept, the pixel mayinclude at least one transistor including silicon. In addition, thefirst infrared light may have a first wavelength that is out of awavelength band of light that is absorbed by the silicon.

According to an embodiment of the inventive concept, the display devicemay further include a scan driver configured to generate a scan signal,and a data driver configured to generate the data signal based on imagedata that is provided from an external device. In addition, the pixelmay include a light emitting element connected between a first powervoltage and a second power voltage, a first transistor configured tocontrol a driving current that flows through the light emitting elementin response to a first node voltage of a first node, a second transistorconfigured to transfer the data signal to the first node in response tothe scan signal, and a storage capacitor connected to the first node andconfigured to store the data signal. Further, the at least onetransistor may include the first transistor and the second transistor.

According to an embodiment of the inventive concept, a first leakagecurrent may flow through the at least one transistor in a turned-offstate when the first infrared light is applied to the active region, asecond leakage current may flow through the at least one transistor inthe turned-off state when natural light is applied to the active region,and a difference between the first leakage current and the secondleakage current may be smaller than or equal to a reference value by thefirst wavelength of the first infrared light.

According to an embodiment of the inventive concept, the infraredsensing module may include an infrared light emitting element configuredto emit the first infrared light, an infrared sensing element configuredto measure intensity of the second infrared light to output ameasurement signal, and an infrared sensing controller configured torecognize the object based on a change of the measurement signal.

According to an embodiment of the inventive concept, the infraredsensing module may further include a condensing lens configured tocondense and output the first infrared light.

According to an embodiment of the inventive concept, the infraredsensing module may include an infrared light emitting element configuredto emit third infrared light, a first infrared transmission filterconfigured to pass the first infrared light included in the thirdinfrared light, an infrared sensing element configured to measureintensity of the second infrared light to output a measurement signal,and an infrared sensing controller configured to recognize the objectbased on a change of the measurement signal.

According to an embodiment of the inventive concept, the infraredsensing module may further include a second infrared transmission filterconfigured to pass fourth infrared light included in the second infraredlight, the fourth infrared light having a wavelength that is equal to awavelength of the first infrared light. In addition, the infraredsensing element may measure intensity of the fourth infrared light.

According to an embodiment of the inventive concept, the display panelmay include a first region through which the first infrared lightpasses, and first pixel density of the first region may be lower thansecond pixel density of a second region that is different from the firstregion.

According to an embodiment of the inventive concept, the first regionmay include a transmission region having transmittance that is higherthan transmittance of the second region.

According to an embodiment of the inventive concept, a display devicemay include a display panel including an active region in which a pixelthat emits light based on a data signal is disposed, and an infraredsensing module configured to transmit first infrared light that passesthrough the active region and to receive second infrared light thatpasses through the active region to recognize an object. Here, the pixelmay include at least one transistor that operates in response to thedata signal, and a current that flows through the at least onetransistor when the at least one transistor is turned off is changedaccording to a change in a wavelength of light that is applied to theactive region. In addition, the first infrared light may have a firstwavelength by which a change rate of the current is smaller than ofequal to a reference value.

According to an embodiment of the inventive concept, the infraredsensing module may include at least one selected from a proximitysensor, a gesture sensor, and a fingerprint recognition sensor.

According to an embodiment of the inventive concept, the at least onetransistor may include (e.g. may be comprised of) silicon. In addition,the first wavelength of the first infrared light may have a wavelengththat is out of a band of wavelengths of light that the silicon absorbs.

According to an embodiment of the inventive concept, the firstwavelength of the first infrared light may be greater than 1200 nm.

According to an embodiment of the inventive concept, the firstwavelength of the first infrared light may be about 1300 nm.

Therefore, a display device according to example embodiments may includea display module that displays an image on an entire region of its frontsurface and an infrared sensing module that is located on a back surfaceof the display module. Here, the infrared sensing module may transmitfirst infrared light that passes through the display module to go theoutside of the display device (e.g., an exterior) and may recognize anobject based on second infrared light that passes through the displaymodule to go inside the display device (e.g. an interior), where one ormore various types of sensors detect, for example, the presence of anobject external to the display device, and/or various attributes orcharacteristics of the object, including but not limited to distancefrom the display device, gestures, biometric information (included butnot limited to fingerprint, iris, facial scanning). In particular, sincethe first infrared fight may have a first wavelength of more than 1200nm (e.g., 1200 nm, 1300 nm, etc), luminance of a pixel located in aspecific region of the display module may not be changed although thefirst infrared light passes through the specific region of the displaymodule. Thus, the display device may display the image normally on thefront surface of the display device while including an infrared sensingfunction.

In addition, in the display device, the specific region of the displaymodule (e.g., a portion of a display panel) through which the firstinfrared light passes may have relatively low pixel density or may bepartially transparent. Thus, transmittance of the first infrared lightmay be enhanced and thus recognition of the display device for theobject may be increased.

According to an embodiment of the inventive concept, a display panel mayinclude an active region in which a pixel is disposed, the pixel emitslight based on a data signal; and an infrared sensing module configuredto transmit a first infrared light that passes through the active regionto exit the display device, and to receive a second infrared light thatenters the display device and passes through the active region torecognize an object. The pixel may include at least one transistor thatoperates in response to receiving the data signal, and a current thatflows through the at least one transistor when the at least onetransistor is turned off is changed according to a change in awavelength of light that is applied to the active region. The firstinfrared light may have a first wavelength having a change rate of thecurrent that is less than or equal to a reference value.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more illustrative, non-limiting embodiments will be betterappreciated by a person of ordinary skill in the art from the followingdetailed description taken in conjunction with the accompanyingdrawings.

FIGS. 1A and 1B are diagrams illustrating a display device according toan embodiment of the inventive concept.

FIG. 2 is a block diagram illustrating an example of the display deviceof FIGS. 1A and 1B.

FIG. 3 is a block diagram illustrating an example of a display moduleincluded in the display device of FIG. 2.

FIG. 4 is a circuit diagram illustrating an example of a pixel includedin the display module of FIG. 3.

FIG. 5A is a diagram illustrating a leakage current of transistorsincluded in the pixel of FIG. 4.

FIG. 5B is a diagram illustrating characteristics of silicon transistorsincluded in the pixel of FIG. 4.

FIG. 5C is a diagram illustrating an example in which the leakagecurrent of FIG. 5A is changed according to a wavelength of infraredlight.

FIG. 6 is a block diagram illustrating an example of an infrared sensingmodule included in the display device of FIG. 2.

FIGS. 7A and 7B are diagrams illustrating an example of a display panelincluded in the display module of FIG. 3.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present inventive concept will beexplained in detail with reference to the accompanying drawings.

FIGS. 1A and 1B are diagrams illustrating a display device according toan embodiment of the inventive concept. FIG. 2 is a block diagramillustrating an example of the display device of FIGS. 1A and 1B.

Referring now to FIGS. 1A, 1B, and 2, the display device 100 may includea display module 110, an infrared sensing module 120, and an applicationprocessor 130. For example, the display device 100 may be a smart phone.

The display module 110 may display an image based on image data. Here,the display module 110 may display the image on an entire region of itsfront surface (e.g., a surface of the display module 110 in a firstdirection D1). The entire front surface (without a border or bezel) maybe used for display of an image. In other words, the entire region ofthe front surface of the display module 110 may be an active region inwhich pixels are arranged, and thus the display module 110 may notinclude a bezel (e.g., referred to as a dead space, an inactive region,etc) on its front surface.

The infrared sensing module 120 (shown in FIG. 1B) may be located on aback surface of the display module 110 (e.g., a rear surface of thedisplay module 110 in a direction opposite to the first direction D1).In other words, the infrared sensing module 120 may be located betweenthe display module 110 and a case 140 (or, a cover, a housing, etc.).Here, the case 140 may provide an outward form of the display device 100and may protect internal components (e.g., a battery, a memory device,etc) against external shocks (or, external stresses).

The infrared sensing module 120 may transmit first infrared light L1,may receive second infrared light L2, and may recognize an object 200based on a change of the second infrared light L2. Here, the firstinfrared light L1 may travel in the first direction D1 and may passthrough a first region A1 of the display module 110. In addition, thesecond infrared light L2 may include reflected light that is generatedby at least a portion of the first infrared light L1 being reflected offof the object 200, may travel in the direction opposite to the firstdirection D1, and may pass through the first region A1 of the displaymodule 110.

The infrared sensing module 120 may be arranged such that a portion fromwhich the infrared light is transmitted may face the rear surface of thedisplay panel to transmit the first infrared light through a portion ofthe display panel that exits the front surface of the display panel. Theportion of the display panel may be an active region, or another regionhaving a lower pixel density than a remainder of the active region. Forexample, the other region may be a region where the display panel issubstantially transparent. An artisan should understand and appreciatethat the display device 100 may have more than one infrared sensingmodule 120. A plurality of infrared sensing modules 120 could be locatedon or facing the rear surface of the display panel in areas having lowerpixel density or transparency than an active region. For example,infrared sensing modules 120 could be arranged, as shown in FIG. 1A nearupper and lower edges of the rear surface of the display panel. Theinfrared sensing modules 120 may also be arranged along lateral edges ofthe rear surface of the display panel.

In an embodiment of the inventive concept, the infrared sensing module120 may include one or more types of sensors, and the one or more typessensors may comprise, for example, a proximity sensor, a gesture sensor,a fingerprint recognition sensor, and/or an iris recognition sensor,etc., just to name some non-limiting possible examples of various typesof sensors. Moreover, for example, the proximity sensor may detect alocation of the object 200 (e.g., a distance between the object 200 andthe display device 100) when the object 200 approaches the displaydevice 100. The gesture sensor, for example, may sense infrared lights(or, intensities of the infrared lights, infrared energies) of aplurality of points (e.g., a plurality of points on the front surface ofthe display device 100) and may detect a motion of the object 200 (or, amoving direction, a moving distance, a moving speed, a moving pattern, agesture, etc) based on changes of the infrared lights. The fingerprintrecognition sensor may generate an image of a fingerprint of a userbased on the infrared light and may recognize the fingerprint of theuser by analyzing a contrast pattern of the image. The iris recognitionsensor may generate a picture of an iris of a user based on the infraredlight and may recognize the iris of the user by analyzing a contrastpattern of the picture.

The wavelength of the first infrared light L1 may be a wavelengthgreater than a predetermined value so that a luminance of light emittedby the pixel is not affected by operation of the infrared sensing module120. The predetermined value of the wavelength may be, for example, 1200nm. However, the inventive concept is not limited to such a value.

For example, in at least one embodiment of the inventive concept, thefirst infrared light L1 may have a first wavelength of more than about1200 nm. For example, the first wavelength of the first infrared lightL1 may be about 1300 nm.

Each of the pixels arranged in the display module 110 may include atransistor, and the transistor may have different characteristicsaccording to a wavelength of incident light. For example, an amount of aleakage current that flows through the transistor (e.g., an amount of acurrent that flows through the transistor when the transistor is turnedoff) may change according to the wavelength of the incident light. Thesecharacteristics will be described in more detail with reference to FIGS.4, 5A, 5B, and 5C. Accordingly, based on the same data signal, a pixelin the first region A1 of the display module 110, where the first andsecond infrared lights L1 and L2 pass through the first region A1 of thedisplay module 110, may emit light having luminance different from thatof light emitted by a pixel in another region of the display module 110(e.g., a region other than the first region A1 in the display module 110or a region through which only natural light passes).

When the first infrared light L1 has the first wavelength of greaterthan 1200 nm, an amount (or, a rate) of a change in the leakage currentof the transistor included in the first region A1 may be sharplyreduced. In addition, when the first infrared light L1 has the firstwavelength of 1300 nm, the amount (or, a rate) of change in the leakagecurrent of the transistor included in the first region A1 may stay thesame (e.g. no change in the rate).

A structure of the infrared sensing module 120 will be described indetail with reference to FIG. 6. The first wavelength of the firstinfrared light L1 will be described in detail with reference to FIGS. 5Athrough 5C.

The application processor 130 may include a function that executesapplication programs an operating system (OS) of the display device 100(e.g., a smart phone, a tablet PC, etc) and a function that controlsexternal system devices and/or interfaces.

In an embodiment of the inventive concept, the application processor 130may control operation of the display module 110 and the infrared sensingmodule 120. For example, the application processor 130 may stop anoperation of the display module 110 when the infrared sensing module 120recognizes the object 200 (or, when the object 200 approaches thedisplay module 110). For example, the application processor 130 may stopan operation of the infrared sensing module 120 and may control thedisplay module 110 to operate regardless of whether the object 200 isrecognized.

In brief, the display device 100 may include the display module 110 thatdisplays the image on the entire region of its front surface and theinfrared sensing module 120 that is located on the rear (e.g. back)surface of a display panel of the display module 110. The infraredsensing module 120 may transmit the first infrared light L1 that passesthrough the display module 110 and may recognize the object 200 based onthe second infrared light L2 that passes through the display module 110.Here, since the first infrared light L1 has the first wavelength of morethan 1200 nm, the pixels in the first region A1 of the display module110 may operate normally although the first infrared light L1 passesthrough the first region A1 of the display module 110. Thus, the displaydevice 100 may display the image normally on its front surface (e.g. afront surface of a display panel) while including an infrared sensingfunction.

FIG. 3 is a block diagram illustrating an example of a display moduleincluded in the display device of FIG. 2. FIG. 4 is a circuit diagramillustrating an example of a pixel included in the display module ofFIG. 3. A structure of the display module 110 will now be described indetail with reference to FIG. 3.

Referring to FIG. 3, the display module 110 may include a display panel310, a timing controller 320, a scan driver 330, and a data driver 340.

The timing controller 320 may, for example, control the scan driver 330and the data driver 340 by receiving input data (e.g., first data DATA1)and input control signals (e.g., a horizontal synchronization signal, avertical synchronization signal, and clock signals) from an externaldevice, by generating image data (e.g., second data DATA2) suitable forimage displaying by a display panel of the display module 110, and bygenerating a scan driving control signal SCS and a data driving controlsignal DCS based on the input control signals.

The scan driver 330 may generate a scan signal based on the scan drivingcontrol signal SCS received from the timing controller 320. The scandriving control signal SCS may include a start pulse and clock signals.The scan driver 330 may include shift registers that sequentiallygenerate the scan signal based on the start pulse and the clock signals.

The data driver 340 may generate a data signal based on the data drivingcontrol signal DCS. The data driver 340 may convert the image data froma digital data signal into an analog data signal. The data driver 340may generate the data signal corresponding to the image data (e.g., datavalues included in the image data) based on predetermined gray-scalevoltages (or, predetermined gamma voltages) and may sequentially providethe data signal to the display panel of the display module 110.

With continued reference to FIG. 3, the display panel of display module110 may include scan-lines S1 through Sn, data-lines D1 through Dm, andpixels PX, where n and m are integers greater than or equal to 2. Thepixels PX may be arranged at locations corresponding to intersectingpoints of the scan-lines S1 through Sn and the data-lines D1 through Dm.Each of the pixels PX may store the data signal that is provided throughthe data-lines D1 through Dm in response to the scan signal that isprovided through the scan-lines S1 through Sn and may emit light basedon the stored data signal.

The display panel 310 may be disposed on the front surface of thedisplay module 110 (or, the display device 100), and thus only a frontsurface of the display panel 310 may be exposed to the outside. Inaddition, the timing controller 320, the scan driver 330, and the datadriver 340 may be located on a back (e.g. rear) surface of the displaypanel 310.

Referring now to FIG. 4, the pixel 400 may include a light emittingelement EL, a first transistor T1, a second transistor T2, and a storagecapacitor Cst.

The light emitting element EL may be connected, for example, between afirst power voltage ELVDD and a second power voltage ELVSS. Here, thefirst power voltage ELVDD may be greater than the second power voltageELVSS. The light emitting element EL may emit light based on an amountof a driving current that flows through the light emitting element ELbetween the first power voltage ELVDD and the second power voltageELVSS. In addition, the light emitting element EL may be an organiclight emitting diode. However, a person of ordinary skill in the artshould understand and appreciate that the inventive concept is notlimited to a particular type of light emitting element. Here, the firstand second power voltages ELVDD and ELVSS may be generated by a powersupply 350 illustrated in FIG. 3.

The first transistor T1 may include a first electrode that is connectedto the first power voltage ELVDD, a second electrode that is connectedto the light emitting element EL (e.g., an anode of the light emittingelement EL), and a gate electrode that is connected to a first node N1.The first transistor T1 may control the driving current (e.g., an amountof the driving current) in response to a first node voltage of the firstnode N1 to open and close the gate of the first transistor T1.

The second transistor T2 may include a first electrode that receives thedata signal Vdata, a second electrode that is connected to the firstnode N1, and a gate electrode that receives the scan signal scan[n]. Thesecond transistor T2 may transfer the data signal Vdata to the firstnode N1 in response to a voltage level of the scan signal scan[n].

The storage capacitor Cst may be connected between the first node N1 andthe first power voltage ELVDD. The storage capacitor Cst may store thedata signal Vdata transferred via the second transistor T2.

Although it is illustrated in FIG. 4 that the pixel 400 includes thefirst and second transistors T1 and T2 and the storage capacitor Cst,the inventive concept is not limited to pixels having the structure aspixel 400. For example, the pixel 400 may have a 7T-1C structureincluding seven transistors and one capacitor. Although it isillustrated in FIG. 4 that the first and second transistors T1 and T2 ofthe pixel 400 are implemented by P-type transistors, the first andsecond transistors T1 and T2 of the pixel 400 may be implemented byN-type transistors. The aforementioned are just a few of the possiblearrangements according to the inventive concept.

As described above, the pixel 400 may exhibit different characteristicsaccording to a particular wavelength of light that enters (or, passesthrough) the pixel 400 (e.g., incident light). For example, even whenthe pixel 400 receives the same data signal, the pixel 400 may emitlight having different luminance according to the wavelength of theincident light. For example, luminance implemented by a pixel to whichinfrared light having a wavelength of 940 nm (e.g., infrared lighttransmitted by a conventional infrared sensor) is applied may bedifferent from luminance implemented by the pixel to which natural lightis applied.

In the embodiment shown in FIG. 4, a person of ordinary skill in the artshould appreciate that the pixel 400 includes the light emitting elementEL, the first and second transistors T1 and T2, and the storagecapacitor Cst, a change in characteristics of the pixel 400 may becaused by the light emitting element EL, the first and secondtransistors T1 and T2, and the storage capacitor Cst. Hereinafter, thechange in characteristics of the pixel 400 will be described in detailwith reference to experimental examples.

First Experimental Example

In a first case where infrared light was not applied to the pixel 400(or, when only the natural light is applied to the pixel 400), firstluminance (e.g., reference luminance) implemented by the light emittingelement EL of the pixel 400 was measured. As the infrared light havingthe wavelength of 940 nm was applied to just the light emitting elementEL of the pixel 400, a second luminance implemented by the lightemitting element EL of the pixel 400 was measured. In this case, thefirst luminance was equal to the second luminance.

The second luminance implemented by the light emitting element EL of thepixel 400 was measured by changing the wavelength of the infrared lightthat is applied to the light emitting element EL of the pixel 400 amongvarious wavelengths, which were, for example 625 nm, 880 nm, 970 nm,1050 nm, 1200 nm, 1300 nm, and 1450 nm. In this case, the firstluminance was equal to the second luminance.

In conclusion, from the first experimental example, it was confirmedthat the light emitting element EL of the pixel 400 was not affected bythe infrared light (e.g., the wavelength of the infrared light).

Second Experimental Example

The infrared light was applied to just the storage capacitor Cst of thepixel 400. Here, the second luminance implemented by the light emittingelement EL of the pixel 400 was measured by changing the wavelength ofthe infrared light that is applied to the storage capacitor Cst of thepixel 400. In this case, the first luminance was equal to the secondluminance.

In conclusion, from the [second experimental example], it was confirmedthat the storage capacitor Cst of the pixel 400 was not affected by theinfrared light (e.g., the wavelength of the infrared light).

Third Experimental Example

As the infrared light was not applied to the pixel 400, a first leakagecurrent of the first transistor T1 of the pixel 400 (e.g., a leakagecurrent flowing through the first transistor T1 when the firsttransistor T1 is turned off) was measured. As the infrared light havingthe wavelength of 940 nm was applied to only the first transistor T1 ofthe pixel 400, a second leakage current of the first transistor T1 ofthe pixel 400 was measured, and a graph is provided to illustrate theresponse.

FIG. 5A is a diagram illustrating a leakage current of transistorsincluded in the pixel of FIG. 4.

Referring to FIG. 5A, a gate voltage VGS refers to a voltage applied toa gate electrode of the first transistor T1 (or, a voltage between thegate electrode and a source electrode in the first transistor T1), and acurrent IDS refers to a current flowing through the first transistor T1.

The first curve G1 indicates the first current flowing through the firsttransistor T1 when the infrared light was not applied to the pixel 400.The second curve G2 indicates the second current flowing through thefirst transistor T1 when the infrared light having the wavelength of 940nm was applied to only the first transistor T1.

As illustrated in FIG. 5A, the second current was equal to the firstcurrent when the gate voltage VGS was less than −5 volt (V), moreaccurately, less than −3 volt (e.g., when the P-type transistor wasturned on).

On the other hand, the second current was different from the firstcurrent when the gate voltage VGS was more than −0 volt, moreaccurately, more than −3 volt (e.g., when the P-type transistor isturned off). As illustrated in FIG. 5A, When the gate voltage VGS was 0volt, the second current was about 1.E-14 (e.g., 10⁻¹⁴) ampere (A) andthe first current was about 1.E-11 (e.g., 10⁻¹¹) ampere. In other words,the leakage current of the first transistor T1 was increased.

In conclusion, from the third experimental example and FIG. 5A, it wasconfirmed that the first transistor T1 of the pixel 400 was affected bythe infrared light (e.g., the wavelength of the infrared light).

Similarly, the second transistor T2 was experimented under the samecondition as that of the third experimental example. As a result, theleakage current of the second transistor T2 was similar to the leakagecurrent of the first transistor T1. In conclusion, from the thirdexperimental example and FIG. 5A, it was confirmed that the secondtransistor T2 of the pixel 400 was affected by the wavelength ofinfrared light.

For reference, the first and second transistors T1 and T2 may includesilicon (Si), and the silicon may absorb light having a specificwavelength band. Thus, it was assumed that characteristics of thesilicon changed characteristics of the first and second transistors T1and T2. Based on this assumption, the third experimental example wasrepeatedly performed by changing the wavelength of the infrared light.

FIG. 5B is a diagram illustrating characteristics of silicon oftransistors included in the pixel of FIG. 4.

Referring to FIG. 5B, a third curve G3 indicates an ideal spectralresponse of the silicon, and a fourth curve G4 indicates an actualspectral response of the silicon.

The silicon absorbed light having a first wavelength band between 0micrometer (μm) (or, in some embodiments of the inventive concept, 0.01μm or 10 nanometer (nm)) and 1.1 μm along the third curve G3. As awavelength was longer in the first wavelength band, an amount of lightabsorbed by the silicon was increased.

The silicon absorbed light having a second wavelength band between 0.4μm (or, 400 nm) and 1.2 μm (or, 1200 nm) along the fourth curve G4.Here, the silicon absorbed most of light having a wavelength of 1 μm,and thus an absorption amount of light having a wavelength of more than1 μm was sharply decreased. The energy gap (or, band gap) of the siliconwas 1.12 electron volt (eV) corresponding to light having a wavelengthof about 1.1 μm (or, 1100 nm).

Fourth Experimental Example

When the wavelength of the first infrared light L1 was out of the secondwavelength band (e.g., a wavelength band between 0.4 μm and 1.1 μm),assuming that the leakage current of the first transistor T1 (or, thesecond transistor T2) was not changed, the fourth experimental examplewas repeatedly performed by changing the wavelength of the infraredlight.

More specifically, as the infrared light was not applied to the pixel400, the first leakage current of the first transistor T1 (e.g., theleakage current flowing through the first transistor T1 when the firsttransistor T1 was turned off) was measured. In addition, as the infraredlight was applied to only the first transistor T1, the second leakagecurrent of the first transistor T1 was measured. Here, the secondleakage current was repeatedly measured by changing the wavelength ofthe infrared light among 625 nm, 880 nm, 970 nm, 1050 nm, 1200 nm, 1300nm, and 1450 nm.

FIG. 5C is a diagram illustrating an example in which the leakagecurrent of FIG. 5A is changed according to a wavelength of infraredlight.

Referring to FIG. 5C, a fifth curve G5 indicates a current differenceΔIOFF between a first leakage current and a second leakage currentaccording to a wavelength.

Along the fifth curve G5, the current difference ΔIOFF was 1.E-13 amperewhen the wavelength of the infrared light was 625 nm, the currentdifference ΔIOFF was reduced when the wavelength of the infrared lightwas 1050 nm, the current difference ΔIOFF was sharply reduced when thewavelength of the infrared light was 1200 nm (e.g., the currentdifference ΔIOFF when the wavelength of the infrared light was 1200 nmwas less than 1/20 of the current difference ΔIOFF when the wavelengthof the infrared light was 1050 nm), and the current difference ΔIOFF wasless than 1.E-16 (or, zero) ampere when the wavelength of the infraredlight was more than 1300 nm (e.g., 1300 nm, 1450 nm, etc). For example,the current difference ΔIOFF when the wavelength of the infrared lightwas 625 nm had the greatest value, and the current difference ΔIOFF whenthe wavelength of the infrared light was more than 1300 nm had thesmallest value.

In brief, the current difference ΔIOFF shown in FIG. 5C when thewavelength of the infrared light was 1200 nm was significantly reducedas compared to the current difference ΔIOFF when the wavelength of theinfrared light was less than 1200 nm. In addition, the leakage currentof the first transistor T1 was not changed when the wavelength of theinfrared light was more than 1300 nm.

Generally, as an energy (or, a wavelength energy) of the infrared lightis weaker as a wavelength of the infrared light is longer. Thus, as thewavelength of the infrared light is longer, the sensing performance ofthe infrared sensing module 120 that uses the infrared light may bedegraded. In other words, the energy of the infrared light is inverselyproportional to the wavelength of the infrared light. Thus, the firstinfrared light L1 may have a wavelength included in a wavelength bandbetween 1200 nm and 1400 nm corresponding to a range of energy reductionof less than 30%.

In an embodiment of the inventive concept, the first infrared light L1may have a wavelength of 1200 nm. In this case, the energy of the firstinfrared light L1 may be maximized while minimizing an amount (or, arate) of a change in the leakage current of the first and secondtransistors T1 and T2 included in the pixel 400 (or, while controlling achange in luminance implemented by the pixel 400 not to be perceived bya user).

In an embodiment of the inventive concept, the first infrared light L1may have a wavelength of 1300 nm. In this case, the energy of the firstinfrared light L1 may be maximized while preventing the change in theleakage current of the first and second transistors T1 and T2 includedin the pixel 400.

As described with reference to FIGS. 4, 5A, 5B, and 5C, although theleakage current of the first and second transistors T1 and T2 is changedaccording to the wavelength of the first infrared light L1 that istransmitted by the infrared sensing module 120 and then input to thepixel 400, the leakage current of the first and second transistors T1and T2 may not change when the first infrared light L1 has a wavelengthof more than 1200 nm. In other words, the pixel 400 may emit lightnormally when the first infrared light L1 has a wavelength of more than1200 nm. In addition, when the first infrared light L1 has a wavelengthof 1200 nm, the sensing performance of the infrared sensing module 120may be maximized while controlling the change in luminance implementedby the pixel 400 not to be perceived by the user. Further, when thefirst infrared light L1 has a wavelength of 1300 nm, the first infraredlight L1 may not affect the pixel 400.

FIG. 6 is a block diagram illustrating an example of an infrared sensingmodule included in the display device of FIG. 2.

Referring to FIGS. 2 and 6, the infrared sensing module 120 may include,for example, an infrared sensor 610 and an infrared sensing controller620.

The infrared sensor 610 may include an infrared light emitting element611 and an infrared sensing element 612.

The infrared light emitting element 611 may output (or, transmit) thefirst infrared light L1. For example, the infrared light emittingelement 611 may be an infrared light emitting diode, and the firstinfrared light L1 having a wavelength of more than 1200 nm may beoutput. The infrared light emitting element 611 may be located within asensor case 613. The infrared light emitting element 611 may output thefirst infrared light L1 in a specific direction (e.g., in the firstdirection D1 as illustrated in FIG. 1B).

The infrared sensing element 612 may measure (or, sense) intensity ofthe second infrared light L2 to generate a measurement signal. Here, thesecond infrared light L2 may include reflected light that is generatedby the first infrared light L1 being reflected by the object 200. Asdescribed above, the infrared sensing element 612 may be located withinthe sensor case 613. Here, the infrared sensing element 612 may belocated in a space that is different from a space in which the infraredlight emitting element 611 is located, where the space in which theinfrared sensing element 612 is located may be separated, by an opticalwall 614, from the space in which the infrared light emitting element611 is located.

In an embodiment of the inventive concept, the infrared sensing element612 may be an infrared image-pickup element or an infrared imagingelement. The infrared sensing element 612 may include a plurality ofsensing elements and may generate a two-dimensional (2D) infrared image.In this case, the infrared sensing module 120 may be a fingerprintrecognition sensor or an iris recognition sensor.

In an embodiment of the inventive concept, the infrared sensor 610 mayfurther include a condensing lens. Here, the condensing lens may bedisposed over the infrared light emitting element 611 (or, on the pathalong which the first infrared light L1 output from the infrared lightemitting element 611 travels). In this case, the energy of the firstinfrared light L1 may be strengthened (or, increased).

In an embodiment of the inventive concept, the infrared sensor 610 mayfurther include a first infrared transmission (or, a penetration) filter615. Here, the first infrared transmission filter 615 may be disposedover the infrared light emitting element 611 (or, on the path alongwhich the first infrared light L1 output from the infrared lightemitting element 611 travels). Thus, the first infrared transmissionfilter 615 may allow only the first infrared light L1 having awavelength of more than 1200 nm (or, 1300 nm) to pass through. In thiscase, the infrared light emitting element 611 may emit third infraredright having a wavelength of less than 1200 nm, but the infrared sensor610 may emit only the first infrared light having a wavelength of morethan 1200 nm using the first infrared transmission filter 615.

In an embodiment of the inventive concept, the infrared sensor 610 mayfurther include, for example, a second infrared transmission filter 616.Here, the second infrared transmission filter 616 may be disposed overthe infrared sensing element 612 (or, on the path along which the secondinfrared light L2 input to the infrared sensing element 612 travels).Thus, the second infrared transmission filter 616 may allow only fourthinfrared light L4 (e.g., the reflected light that is generated by thefirst infrared light L1 being reflected by the object) having awavelength of more than 1200 nm (or, 1300 nm) to pass through. In thiscase, the infrared sensing element 612 may generate (or, output) themeasurement signal through more simple processes. For example, theinfrared sensing element 612 may exclude a process of extracting thereflected from the second infrared light L2.

The infrared sensing controller 620 may control an operation of theinfrared sensor 610 and may recognize the object 200 based on themeasurement signal (or, a change of the measurement signal). Forexample, the infrared sensing controller 620 may control an operatingstate, an operating cycle, etc of the infrared sensor 610 based on acontrol signal that is externally provided (e.g., a control signal thatis provide from the application processor 130 of FIG. 2). In addition,as described above with reference to FIG. 1, the infrared sensingcontroller 620 may recognize (or, detect) a location of the object 200(e.g., a distance between the object 200 and the display device 100)based on the measurement signal or may recognize a motion (or, movement)of the object 200 based on the change of the measurement signal. Inaddition, when the infrared sensing element 612 is the infraredimage-pickup element, the infrared sensing element 612 may recognize aspecific pattern (e.g., a fingerprint pattern, an iris pattern, etc)from an infrared image.

FIGS. 7A and 78 are diagrams illustrating an example of a display panel310 included in the display module 110 of FIG. 3.

Referring to FIGS. 3 and 7A, first pixel density of the first region A1may be lower than second pixel density of the second region A2. Asdescribed above with reference to FIG. 1B, the first infrared light L1may be applied to the first region A1. In the display module 110 (or, anactive region of the display panel 310 illustrated in FIG. 3), thesecond region A2 may be a region other than the first region A1.

For example, a size of a first pixel PX1 included in the first region A1may be bigger than a size of a second pixel PX2 included in the secondregion A2. For example, the size of the first pixel PX1 may be fourtimes bigger than the size of the second pixel PX2. For example, thefirst pixel PX1 and the second pixel PX2 include an identical pixelcircuit (e.g., the transistors T1 and T2, the light emitting element EL,etc included in the pixel 400 illustrated in FIG. 4). But, the firstpixel PX1 may further include an empty space in which components likewirings, transistors, etc are not formed. Thus, the light passingthrough the empty space of the fast pixel PX1 may not be reflected orblocked by the components.

Referring to FIG. 7B, the first region A1 may include a transmissionregion TA (or, a transmission window). Here, the transmission region TAof the first region A1 may have transmittance higher than transmittanceof the second region A2 (or, a region in which sub pixels R, G, and Bthat emit first color light, second color light, and third color light,respectively are formed).

For example, the transmission region TA may be located near the subpixels R, G, and B, and the pixel circuit (e.g., electrodes, wirings,transistors, etc) may not be formed in the transmission region TA. Forexample, an area of the transmission region TA may be about 20%˜90% ofan area of the first region A1. For example, the first region A1 may bepartially transparent. Thus, most of the first infrared light L1 inputto the transmission region TA may pass through the transmission regionTA.

As described above with reference to FIG. 5C, as the wavelength of thefirst infrared light L1 is longer, the energy of the first infraredlight L1 array be weaker. Thus, the first infrared light L1 may be lost(or, disappeared) as the first infrared light L1 passes through thedisplay panel 310. Thus, the display panel 310 (or, the first region A1)may be partially transparent and thus sensing performance (or, sensingaccuracy, recognition rate) of the infrared sensing module 120 may beenhanced.

As described above with reference to FIGS. 7A and 7B, the first pixeldensity of the first region A1 through which the first infrared light L1passes (e.g., the first region A1 of the display panel 310) may be lowerthan a pixel density of another region. For example, the first region A1may be partially transparent. Thus, transmittance of the first infraredlight L1 may be enhanced (or, increased), and thus the recognition rateof the infrared sensing module 120 may be prevented from being degraded(or, decreased).

The present inventive concept may be applied to a display device andvarious display systems including the display device. For example, thepresent inventive concept may be applied to a television, a computermonitor, a laptop, a digital camera, a cellular phone, a smart phone, avideo phone, a smart pad, a smart watch, a tablet PC, a car navigationsystem, a personal digital assistants (PDA), a portable multimediaplayer (PMP), an MP3 player, etc.

The foregoing is illustrative of one or more embodiments of theinventive concept and is not to be construed as limiting thereof.Although a few embodiments of the inventive concept have been describedherein, those skilled in the art will readily appreciate that manymodifications are possible in the discussed embodiments withoutmaterially departing from the novel teachings and advantages of thepresent inventive concept. Accordingly, all such modifications areintended to be included within the scope of the present inventiveconcept as defined in the claims. Therefore, it is to be understood thatthe foregoing is illustrative of various embodiments of the inventiveconcept and is not to be construed as limited to the specific embodimentdiscussed herein, and that modifications to the embodiments discussedherein, as well as in other embodiments, are intended to be includedwithin the scope of the appended claims.

What is claimed is:
 1. A display device comprising: a display panelhaving a front surface and a rear surface, the display panel includingan active region in which a pixel that emits light based on a datasignal is disposed, and the active region including a first region and asecond region that is different from the first region; and an infraredsensing module that transmits a first infrared light that passes in afirst direction away from the front surface of the display panel andthrough the first region of the active region, and that receives asecond infrared light that passes in a second direction toward the frontsurface of the display panel and through the first region of the activeregion by which the infrared sensing module recognizes an objectexternal to the display device, wherein a first pixel density of thefirst region of the active region is lower than a second pixel densityof the second region of the active region, wherein the pixel includes atleast one transistor comprising silicon, and wherein the first infraredlight has a first wavelength that is outside of a wavelength band oflight that is absorbed by the silicon.
 2. The display device of claim 1,wherein a size of the pixel included in the first region of the activeregion is bigger than a size of the pixel included in the second regionof the active region.
 3. The display device of claim 2, wherein a sizeof a light emitting element of the pixel included in the first region ofthe active region is different from a size of a light emitting elementof the pixel included in the second region of the active region.
 4. Thedisplay device of claim 2, wherein the pixel included in the firstregion of the active region includes an empty space through which thefirst and second infrared lights pass.
 5. The display device of claim 1,wherein the first region of the active region includes at least onetransmission region, and the first region of the active region ispartially transparent by the transmission region.
 6. The display deviceof claim 5, wherein an area of the transmission region is 20%˜90% of anarea of the first region of the active region.
 7. The display device ofclaim 1, wherein the infrared sensing module is disposed on a rearsurface of the display panel, and wherein the infrared sensing moduletransmits the first infrared light in the first direction that issubstantially perpendicular to the front surface of the display panel.8. The display device of claim 1, further comprising a housing having asurface that faces the rear surface of the display panel, wherein theinfrared sensing module is disposed between the rear surface of thedisplay panel and the housing.
 9. The display device of claim 1, whereinthe second infrared light includes reflected infrared light that isgenerated by the first infrared light being reflected by the object, andwherein the infrared sensing module recognizes the object based on achange of the second infrared light.
 10. The display device of claim 1,wherein a luminance of the pixel located in the first region of theactive region is unchanged when the infrared sensing module transmitsthe first infrared light through the first region of the active regionand when the infrared sensing module receives the second infrared lightthrough the first region of the active region.
 11. The display device ofclaim 1, Wherein the infrared sensing module includes: an infrared lightemitting element that emits the first infrared light; an infraredsensing element that measures intensity of the second infrared light tooutput a measurement signal; and an infrared sensing controller circuitrecognizes the object based on a change of the measurement signal. 12.The display device of claim 11, wherein the infrared sensing modulefurther includes: a condensing lens that condenses and outputs the firstinfrared light.
 13. The display device of claim 1, wherein the infraredsensing module includes: an infrared light emitting element that emits athird infrared light; a first infrared transmission filter that passesthe first infrared light included with the third infrared light; aninfrared sensing element that measures intensity of the second infraredlight to output a measurement signal; and an infrared sensing controllercircuit that recognizes the object based on a change of the measurementsignal.
 14. The display device of claim 13, wherein the infrared sensingmodule further includes: a second infrared transmission filter thatpasses a fourth infrared light included with the second infrared light,the fourth infrared light having a wavelength that is equal to awavelength of the first infrared light, and wherein the infrared sensingelement measures an intensity of the fourth infrared light.
 15. Adisplay device comprising: a display panel having a front surface and arear surface, the display panel including an active region in which apixel that emits light based on a data signal is disposed, and theactive region including a first region and a second region that isdifferent from the first region; and an infrared sensing module thattransmits a first infrared light that passes in a first direction awayfrom the front surface of the display panel and through the first regionof the active region, and that receives a second infrared light thatpasses in a second direction toward the front surface of the displaypanel and through the first region of the active region by which theinfrared sensing module recognizes an object external to the displaydevice, the first infrared light having a wavelength of greater than orequal to 1200 nm, wherein a first pixel density of the first region ofthe active region is lower than a second pixel density of the secondregion of the active region, wherein the pixel includes at lest onetransistor comprising silicon, and wherein the wavelength of greaterthan or equal to 1200 nm is outside of a wavelength band of light thatis absorbed by the silicon.
 16. The display device of claim 15, whereina size of the pixel included in the first region of the active region isbigger than a size of the pixel included in the second region of theactive region.
 17. The display device of claim 16, wherein a size of alight emitting element of the pixel included in the first region of theactive region is different from a size of a light emitting element ofthe pixel included in the second region of the active region.
 18. Thedisplay device of claim 16, wherein the pixel included in the firstregion of the active region includes an empty space through which thefirst and second infrared lights pass.
 19. The display device of claim15, wherein the first region of the active region includes at least onetransmission region, and the first region of the active region ispartially transparent by the transmission region.
 20. The display deviceof claim 19, wherein an area of the transmission region is 20%˜90% of anarea of the first region of the active region.